Light emitting device

ABSTRACT

The light emitting device according to the present invention comprises a laser diode; a wavelength converting member which is configured to convert a wavelength of a light emitted from the laser diode; and a support member which is configured to support the wavelength converting member so that the light passes through two surfaces of the wavelength converting member. The wavelength converting member comprises a fluorescent material and a binder. At least one light transmissive member is disposed on at least one of these two surfaces of the wavelength converting member. The binder has a melting point higher than a melting point of the light transmissive member. The light transmissive member is fixed to the support member by fusion bonding.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2013-139674 filed on Jul. 3, 2013 and Japanese Patent Application No.2013-241042 filed on Nov. 21, 2013 the disclosures of which are herebyincorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a light emitting device comprising alaser diode and a wavelength converting member.

2. Background Art

A wavelength converting member generally comprises a binder such asglass, a resin, and the like, in which a fluorescent material isdispersed.

In the case of that glass is used as the binder for the wavelengthconverting member, the wavelength converting member can be secured toother member by, for example, heating, which allows the binder to befused and bonded to the other member (see JP 2010-199357 A).

In the conventional light emitting devices, however, in a case where ahigh output power type laser diode is employed to increase output powerof the light emitting device, the fluorescent material contained in thewavelength converting member may absorb a laser light and then release aheat.

Therefore, the binder surrounding the fluorescent material may bedeformed or discolored.

Furthermore, there are possibilities that the binder may melt due to theheat generation from the fluorescent material, and thus the wavelengthconverting member may be fallen down from the light emitting device.

Herein, object of the present invention consists in a provision of alight emitting device which can employ a high output power type laserdiode as a light source.

SUMMARY OF THE INVENTION

Disclosed herein is a light emitting device comprises

-   -   a laser diode;    -   a wavelength converting member which is configured to convert a        wavelength of a light emitted from the laser diode; and    -   a support member which is configured to support the wavelength        converting member so that the light passes through two surfaces        of the wavelength converting member,        wherein:    -   the wavelength converting member comprises a fluorescent        material and a binder,    -   at least one light transmissive member is disposed on at least        one of the two surfaces of the wavelength converting member,    -   the binder has a melting point higher than a melting point of        the light transmissive member,    -   the light transmissive member is fixed to the support member by        fusion bonding.

The present invention can provide a light emitting device in which ahigh output power type laser diode can be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a light emitting device according toan embodiment of the present invention as a general view.

FIG. 2 is a cross-sectional schematic view of the terminal portion(particularly, components around the support member 3) of the lightemitting device according to an embodiment of the present inventionshown in FIG. 1.

FIG. 3 is a cross-sectional schematic view of the light emitting deviceaccording to the first embodiment of the present invention.

FIG. 4 is a top view of the light emitting device according to the firstembodiment of the present invention.

FIG. 5 is a cross-sectional schematic view of the light emitting deviceaccording to the second embodiment of the present invention.

FIG. 6 is a top view of the light emitting device according to thesecond embodiment of the present invention.

FIG. 7 is a cross-sectional schematic view of the light emitting deviceaccording to the third embodiment of the present invention.

FIG. 8 is a cross-sectional schematic view of the light emitting deviceaccording to the fourth embodiment of the present invention.

FIG. 9 is a cross-sectional schematic view of the light emitting deviceaccording to the fifth embodiment of the present invention.

FIG. 10 is a cross-sectional schematic view of the light emitting deviceaccording to the sixth embodiment of the present invention.

FIG. 11 is a cross-sectional schematic view showing of the lightemitting device according to the other embodiment the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The light emitting device according to the present invention isdescribed hereinafter with referring to the appended drawings.

The light emitting device according to the present invention includes,but is not limited to, the first to the sixth embodiments thereof, forexample, which are described below.

First Embodiment

FIG. 1 is a schematic view showing the light emitting device 10according to the first embodiment of the present invention as a generalview (hereinafter, which can be abbreviated as the “first light emittingdevice”).

FIG. 2 is a cross-sectional schematic view, which further illustratesthe terminal portion (particularly, components around the support member3) of the light emitting device 10 shown in FIG. 1 in detail.

Furthermore, FIG. 3 is a schematic view, which further illustrates indetail, as a cross-sectional schematic view, a relation between thewavelength converting member 2 and the support member 3 in the lightemitting device 10 according to an embodiment of the present invention.FIG. 4 is a plan view of the light emitting device 10 shown in FIG. 3,which is illustrated from a view point above the device 10 (i.e., abovea plane from which a light travels).

As it is illustrated in FIG. 1, FIG. 2 and FIG. 3, the light emittingdevice 10 according to the first embodiment of the present inventioncomprises:

-   -   a laser diode 1, which is configured to oscillate a laser light        (hereinafter, the “laser diode” can be abbreviated as “LD”);    -   a wavelength converting member 2, which is configured to convert        a wavelength of the light emitted from the LD;    -   a support member 3, which is configured to support the        wavelength converting member 2 such that the light emitted from        the LD passes through two surfaces of the wavelength converting        member 2 (e.g., in FIG. 3 which illustrates this embodiment in        detail, these two surfaces include “surface A” (a surface of the        wavelength converting member 2, which is opposed to the surface        directed to the LD) and “surface B” (a surface of the wavelength        converting member 2, which is directed to the LD), both of which        are main surfaces of the member 2, in a pair, and faces each        other).

Herein, the wavelength converting member 2 comprises a fluorescentmaterial and a binder for holding the fluorescent material.

In this embodiment, as the binder contained in the wavelength convertingmember 2, a binder having a melting point higher than that of a lighttransmissive member 4 a or 4 b can be used (hereinafter, the lighttransmissive members 4 a and 4 b can be abbreviated collectively as a“light transmissive member 4”).

Thus, in the case where a binder to be used herein has a relatively highmelting point, the light transmissive member 4 can secure the wavelengthconverting member 2 to the support member 3.

In addition, in the case where the fluorescent material generates anelevated heat due to the LD with improved high output power, thisembodiment can prevent from the deformation and discoloration of thebinder, since the melting of the binder itself can be inhibited.Although the light transmissive member has a melting point lower thanthat of the binder, the light transmissive member is placed apart fromthe fluorescent material.

Therefore, it can prevent the light transmissive member from itsdeformation due to the heat generation from the fluorescent material,etc.

Thus, according to the first embodiment of the present invention, heatresistance of the light emitting device can be improved. Accordingly, alight emitting device having a stable optical property can be provided.

Hereinafter, main components which can be employed in the light emittingdevice 10 are described in detail below.

Laser Diode

The laser diode 1 to be used in the first embodiment of the presentinvention (hereinafter, which is referred to as a “LD”) can be any laserdiode which can oscillate any laser light.

As the LD, a laser diode having an emission peak wavelength within arange, for example, from 300 nm to 500 nm, preferably from 400 nm to 470nm, more preferably from 420 nm to 470 nm can be used. Typically, anedge emitting type LD can be employed herein.

A high output power type LD can be employed as the LD.

For example, an LD having output power from 1 W to 5 W as a single LDcan be used.

Herein, a plurality of LDs can be employed herein to improve the totaloutput power much higher than that in the case where the single LD isemployed.

As it is described above, the light emitting device 10 according to thefirst embodiment of the present invention is particularly effective inthe case of that the high output power type LD is employed, since thedevice has superior heat resistance property.

Herein, the number of the LD to be employed in one single light emittingdevice may be one, or two or more.

In the case of that no less than two LDs are employed, the ranges of thewavelengths may be in the same wavelength band, different from eachother, or partially overlapped with each other.

Wavelength Converting Member

The wavelength converting member 2 includes a fluorescent material and abinder, and has a function converting the wavelength of the lightemitted from the LD.

Thus, the light emitting device, typically, can combine the lightemitted from the LD and the light having the wavelength converted by thewavelength converting member 2 (i.e., the light emitted from thefluorescent material), and then release out the combined light from thislight emitting device.

Shape of the wavelength converting member 2 can be those having twosurfaces through which the light emitted from the LD passes, and theshape is not particularly limited.

For example, as it is shown in FIG. 3, these two surfaces are faced oropposed to each other, each of which is planer (i.e., the wavelengthconverting member 2 is in a shape of a plate).

It may be in other shape, for example, in the shape wherein both of thesurfaces are convex.

In the case of that the wavelength converting member 2 has a shape of aplate, for example, as it is shown in FIG. 3, it is preferable thatthese two surfaces (i.e., “surface A” and “surface B” of FIG. 3) arepositioned in parallel to each other, through which the light emittedfrom the LD passes.

It is also preferable that each of the surfaces A and B of thewavelength converting member 2 is positioned perpendicularly to the axiswhich is in a direction along the traveling direction of the lightemitted from the LD (i.e., “optical axis L”). Although, in FIG. 3, theoptical axis L is illustrated in a linear line for convenience, anoptical fiber 13 as it is shown in FIG. 1 can propagate therethrough thelight emitted from the LD to the wavelength converting member 2 in thisembodiment.

Therefore, spatial relation between the LD and the wavelength convertingmember 2 can be optionally determined, and which is not limited to therelation that the LD and the wavelength converting member 2 are arrangedin a straight line as it is shown in FIG. 3.

The shapes of the surfaces A and B of the wavelength converting member 2from the view point above these two surfaces (or above the plane fromwhich the light travels) are not particularly limited.

The shapes can be, for example, circles and polygons such as triangularand rectangular shapes, etc.

The shape can be optionally or appropriately selected or determineddepending on any application and object of the light emitting device.Herein, dimensions (or areas) of the surfaces A and B in the wavelengthconverting member 2 may be identical or different from each other.

As it is illustrated in FIG. 4 as a plan view from a view point abovethe light emitting device 10, the light emitting device 10 has thewavelength converting member 2 in a rectangular shape, preferably asquare shape, wherein the dimensions of the surfaces A and B areidentical.

The fluorescent material to be contained in the wavelength convertingmember 2 is not particularly limited.

For example, a fluorescent material which can emit a yellow light can beused in the case of that the LD to be employed herein is that oscillatesa blue light.

Thus, it is possible to provide a white light by a combination of thelight emitted from the LD and the light released from the fluorescentmaterial.

Certainly, the light emitted from the LD can be an ultraviolet light. Insuch a case, for example, three fluorescent materials emitting a redlight, a blue light and a green light respectively can be employed inorder to provide a white light by a combination of these three coloredlights released from these three fluorescent materials, respectively.

The fluorescent material includes, for example, ayttrium-aluminium-garnet based fluorescent material (hereinafter, whichcan be referred to as a “YAG type fluorescent material”), alutetium-aluminium-garnet based fluorescent material (hereinafter, whichcan be referred to as a “LAG type fluorescent material”), aterbium-aluminium-garnet based fluorescent material (hereinafter, whichcan be referred to as a “TAG type fluorescent material”), and the like.

The fluorescent material can be employed herein alone or in acombination.

An amount of the fluorescent material to be contained in the wavelengthconverting member 2 is not particularly limited.

For example, it can be within a range from 0.05% to 50%, preferably from1% to 15% by weight relative to the total weight of the wavelengthconverting member 2.

In the case of that the amount is no less than 0.05% by weight, thefluorescent material can convert the light emitted from the LDsufficiently.

In the case of that the amount is no more than 50% by weight, amount ofthe heat resulted from the fluorescent material can be reduced.

The binder to be contained in the wavelength converting member 2 is notparticularly limited.

It is, however, important that the binder is selected to have a meltingpoint higher than that of the light transmissive member as it isdescribed above.

Thus, selecting the binder having such a melting point can prevent thebinder itself from melting, and prevent the binder from deforming and/ordiscoloring, even if the fluorescent material generates heat at hightemperature due to the high output power of the LD.

Furthermore, as the binder having a thermal conductivity superior tothat of the light transmissive member 4 is employed herein, the heatgenerated from the fluorescent material with the higher output power ofthe LD can be successfully dissipated therefrom since the binder canefficiently conduct the heat from the fluorescent material.

Herein, the difference between the melting point of the binder to becontained in the wavelength converting member 2 and the melting point ofthe light transmissive member 4 can be adjusted within a range from 500°C. to 2500° C., preferably from 800° C. to 1500° C.

In the case of that the difference between these melting points is noless than 500° C., the deformation of the binder to be occurred prior tothe deformation of the light transmissive member 4 can be prevented. Inthe case of that the difference between the melting points is no morethan 2500° C., the binder and the light transmissive member 4 can beoptionally and appropriately selected.

The melting point of the binder is generally within a range from 1000°C. to 3000° C., preferably from 1300° C. to 2500° C., more preferablyfrom 1500° C. to 2000° C.

In the case of that the melting point of the binder is no less than1000° C., the deformation of the binder can be prevented during the stepsuch as the fusion bonding of the light transmissive member to thesupport member, and the light transmissive member having a relativelyhigher melting point can be selected.

In the case of that the melting point of the binder is no more than3000° C., the step, for example, formation of the binder by sintering isfacilitated, and therefore, the wavelength converting member with animproved certain quality can be produced.

The binder to be contained in the wavelength converting member 2 can bemade of, for example, aluminium oxide (Al₂O₂, melting point: about 1900°C. to 2100° C.), silicon dioxide (SiO₂, melting point: about 1500° C. to1700° C.), zirconium oxide (ZrO₂, melting point: about 2600° C. to 2800°C.), barium oxide (BaO, melting point: 1800° C. to 2000° C.), titaniumoxide (TiO₂, melting point: 1700° C. to 1900° C.), etc.

Among these, aluminium oxide and silicon dioxide are preferable, and useof the aluminium oxide is particularly preferable because of its meltingpoint, thermal conductivity, diffusibility, etc.

In the present invention, the binder can be composed of one singlematerial, or in a combination of two or more materials. Herein, in thecase of that the binder is composed of two or more materials, themelting point of the binder to be compared to the melting point of thelight transmissive member 4 is defined as the lowest melting point amongthose of the materials.

Herein, the wavelength converting member 2 may optionally comprise alight scattering member.

The light scattering member can be those having a melting point higherthan that of the binder contained in the wavelength converting member 2and having a refractive index different from that of the binder.

Depending on the material to form the binder, the light scatteringmember can be made of, for example, aluminium oxide, silicon oxide,titanium oxide, etc.

Amount of the light scattering member can be smaller than that of thebinder to be employed.

Furthermore, any layer such as an antireflection layer (AR layer) can beoptionally disposed on the surface of the wavelength converting member 2(on the surface directed to the LD, the surface opposed to the surfacedirected to the LD, or on both of these surfaces).

Herein, a plurality of wavelength converting members 2 may be employedin this embodiment.

These wavelength converting members 2 may be identical or different fromeach other.

According to the first embodiment of the present invention, thewavelength converting member 2 can be prepared by mixing the fluorescentmaterial, the binder, and other optional material such as the lightscattering member, and forming the mixture to give a shape having adesired dimension and configuration according to the conventionallyknown method such as sintering.

Light Transmissive Member

The light transmissive member 4 can transmit, therethrough, a lightemitted from a light source, and the light transmissive member 4 can befixed to the support member 3 by fusion bonding.

Optionally, the light transmissive member 4 can at least partially coverthe above-described wavelength converting member 2.

For example, as it is illustrated in FIG. 3, two light transmissivemembers 4 a and 4 b are disposed on both of the light-transmittingsurfaces A and B of the wavelength converting member 2, respectively.Such light transmissive member 4 plays a role which can assist thefixing of the wavelength converting member 2 to the support member 3.

It is preferable that the light transmissive member 4 is fused andbonded to a region in the through-hole 5 of the support member 3predominantly on which the wavelength converting member 2 is notpresented, particularly on an inner wall of the through-hole 5 of thesupport member 3, which is described hereinafter in detail.

Further, it is more preferable that the light transmissive member 4 isalso fused and bonded to the light-transmissive surfaces A and/or B ofthe wavelength converting member 2. It is also preferable that thewavelength converting member 2 which is described hereinafter in detailis not bonded, by its fusion bonding, to the support member 3.

Herein, a conventional general procedure can be employed to bond thewavelength converting member 2 to the support member 3.

For example, the side surface of the wavelength converting member 2 andthe inner wall of the through-hole 5 of the support member 3 can bebonded by a fusion bonding with a low melting glass, etc.

In such a case, however, there may be a problem that the positioning ofthe low melting glass on the support member 3 may be difficult thereon,and the fusion bonding between them may not be performed with a goodreproducibility.

Furthermore, there may be an additional problem that it may be difficultto obtain a sufficient strength of the fusion bonding even in the casewhere the low melting glass can be accurately positioned on the supportmember 3 and the wavelength converting member 2 can be bonded to thesupport member 3, due to the area of the side surface of the wavelengthconverting member 2 is limited.

Herein, in this embodiment, the light transmissive member 4 a can bedisposed on the surface A of the wavelength converting member 2 as it isillustrated in FIG. 3 in detail.

After that, the light transmissive member 4 b can be disposed on thesurface B of the wavelength converting member 2.

Subsequently, the light transmissive members 4 a and 4 b can be fixed tothe support member 3, particularly to the inner wall of the through-hole5 of the support member 3 by fusion bonding, respectively, in order tofix the wavelength converting member 2 to the support member 3.

Placing the light transmissive members 4 a and 4 b on the both surfacesof the wavelength converting member 2 allows the wavelength convertingmember 2 to be fixed more tightly to the support member 3.

Furthermore, in this embodiment, through both of the light transmissivemembers 4 a and 4 b, the heat can be conducted to the support member 3and dissipated therefrom.

Therefore, the heat dissipation from the light emitting device can befurther improved.

The light transmissive member 4 a and/or 4 b may have a refractive indexlower than that of the wavelength converting member 2.

For example, in the case of that the refractive index of the lighttransmissive member 4 a is lower than the refractive index of thewavelength converting member 2, the extraction efficiency of the lightextracted from the light transmissive member 4 a can be improved.

In the case of that the refractive index of the light transmissivemember 4 b is lower than the refractive index of the wavelengthconverting member 2, the incident efficiency of the light entering intothe light transmissive member 4 b can be improved.

The materials to form the light transmissive members 4 a and 4 b can bethose allowing the resulting light transmissive members 4 a and 4 b tobe bonded to the support member 3 by their fusion bonding, respectively.

In the first embodiment of the present invention, it is important toappropriately select the material such that the melting points of thelight transmissive members 4 a and 4 b are respectively lower than themelting point of the binder to be contained in the wavelength convertingmember 2 as it is described above.

The melting point of the light transmissive member can be adjustedwithin a range of generally from 200° C. to 1000° C., preferably from500° C. to 900° C.

In the case of that the melting point is no less than 200° C., someproperties such as heat resistance, weather resistance and transmittanceof the light transmissive member can be improved.

In the case of that the melting point is no more than 1000° C., thefusion bonding of the light transmissive member to the support membercan be facilitated, and therefore, the productivity of this lightemitting device can be improved.

Herein, the melting point of the light transmissive member means atemperature at which softening of the light transmissive member startswith increasing the temperature.

Herein, in the embodiments of the present invention, the melting pointof the light transmissive member is defined as the softening point ofthe main material to form the light transmissive member.

The main material to form the light transmissive member can be glasssuch as soda glass (or soda lime glass), borosilicate glass, lead glass,which are given with preference.

Generally, soda glass means glass comprising silicon dioxide (SiO₂),sodium oxide (Na₂O) and/or potassium oxide (K₂O) as main ingredients. Inthe first embodiment of the present invention, a conventional soda glasscan be used.

Softening point of the soda glass is generally within a range from 500°C. to 800° C., preferably from 600° C. to 800° C.

Generally, the borosilicate glass can be glass comprising silicondioxide (SiO₂) as a main ingredient, and other additional ingredient(s)such as boron oxide (boric anhydride) (B₂O₃).

In the first embodiment of the present invention, the conventionalborosilicate glass can be used.

Softening point of the borosilicate glass is generally within a rangefrom 500° C. to 1000° C., preferably from 500° C. to 900° C.

Generally, the lead glass means glass comprising silicon dioxide (SiO₂)and lead oxide (PbO) as main ingredients.

In the first embodiment of the present invention, the conventional leadglass can be used.

Softening point of the lead glass is generally within a range from 300°C. to 600° C., preferably from 500° C. to 600° C.

It is preferable to use the borosilicate glass because of its lightresistance, weather resistance, transmittance, etc.

Herein, in the case of that the wavelength converting member 2 containsthe light scattering member, as it is described above, a reactionbetween the light scattering member and the binder is occurred duringthe formation of the wavelength converting member 2, and therefore,there is a possibility that the transmittance may be deteriorated.

As it is mentioned above, the wavelength converting member 2 contains agiven amount of the fluorescent material.

Therefore, the content of the light scattering member is limited.

Herein, in this embodiment, the light transmissive member 4 can containthe light scattering member while the wavelength converting member 2contains no light scattering member.

In such a case, local deterioration of the transmittance in thewavelength converting member 2 can be prevented, and the lighttransmissive member 4 can contain the light scattering member in arelatively large amount.

For example, in the case of that the light transmissive member 4 aillustrated in FIG. 3 contains the light scattering member, the lightcan be extracted therefrom in a state of that the light is scattered andthus the light can obtain a desired orientation.

In the case of the light transmissive member 4 b illustrated in FIG. 3contains the light scattering member, the light in a state of that thedensity of the light is lowered can illuminate the fluorescent material.Thus, the heat to be generated from the fluorescent material can bereduced and color unevenness of the extracting light can be improved.

The material of the light scattering member to be contained in the lighttransmissive member 4 is not particularly limited. For example, siliconoxide, titanium oxide or the like can be used.

Herein, the amount of the light scattering member to be contained in thelight transmissive member 4 is not particularly limited.

Herein, optionally, the light transmissive member 4 may contain thefluorescent material in an amount smaller than that of the fluorescentmaterial contained in the wavelength converting member 2 in order tocorrect the color quality of the light entering into the wavelengthconverting member 2 and/or the light extracting from the wavelengthconverting member 2 to obtain the desired color quality.

The fluorescent material may include, but is not particularly limitedto, for example, red fluorescent materials, etc.

In this embodiment, the light transmissive member 4 can be prepared bymixing the material(s) such as those to form the above-described glass,and optional other material(s) such as those to form the lightscattering member, and forming the mixture into the desired shape anddimension.

The light transmissive member 4 can be fixed to the support member 3 by,for example, appropriately positioning the light transmissive member 4together with the wavelength converting member 2 to the support member3, and heating them as a whole to fuse and bond the light transmissivemember 4 to the support member 3.

Herein, the light transmissive member 4 and the wavelength convertingmember 2 may be fixed each other by such fusion bonding. At that time,it is preferable to select the temperature and pressure such that thelight transmissive member 4 is melted while the binder in the wavelengthconverting member 2 is not melted.

Thereby, without the wavelength converting member 2 being melted, thelight transmissive member 4 can be bonded and fixed to the supportmember 3 by the fusion bonding in order to secure the wavelengthconverting member 2 to the support member 3.

Support Member

As it is illustrated in FIG. 3, the support member 3 has a through-hole5 extending along a traveling direction of a light such that a lightemitted from the LD passes through the hole.

The support member 3 can physically support the wavelength convertingmember 2 on the inner wall of the through-hole 5.

As used herein, with respect to the support member 3, the expression the“through-hole 5 extending along with a traveling direction of a light”is defined as that the diameter of the through-hole 5 is getting largeralong with the traveling direction of the light in the first embodimentof the present invention.

The support member 3 comprises:

-   -   a base portion 7 having a through-hole 5 formed approximately        coaxially to the optical axis L, with the base portion being in        the shape of a disk; and    -   a sleeve portion 8 supporting the bottom surface of the base        portion 7 (its surface directed to the LD) at its periphery,        which portion is in the shape of a cylinder.

It is preferable that the base portion 7 and the sleeve portion 8 areformed together integrally in this embodiment.

In this embodiment, the inner wall of the through-hole 5 created in thebase portion 7 of the support member 3 has a tapered surface extendingalong with the traveling direction of the light.

Accordingly, on such tapered surface, the attached area between thesupport member 3 and the light transmissive members 4 a and 4 b isincreased, and the therefore, the bonding strength by the fusion bondingis increased.

Additionally, the tapered surface can prevent the light from goingbackward to the LD.

In this embodiment, the angle of the tapered surface is not particularlylimited, and optionally, depending on the desired application, it can beappropriately determined.

On the inner wall of the through-hole 5, the tapered surface is notprovided on all the inner surface, as it is illustrated in FIG. 3. Onthis inner surface, a stage 6 can be provided to support the wavelengthconverting member 2 thereon.

The stage 6 has a plane perpendicular to the optical axis L, which canfacilitate the positioning of the wavelength converting member 2 on thesupport member 3.

Providing the stage 6 relatively facilitates that the light transmissivemembers 4 a and 4 b are fused and bonded to the inner wall of thethrough-hole 5.

In addition, FIG. 4 is a plan view of the light emitting device 10 whichis illustrated in FIG. 3 from an upper view point (i.e., a view pointabove the surface A of the wavelength converting member 2).

It is preferable that an aperture P of the through-hole 5 directing tothe LD, an aperture Q of the through-hole 5 opposed to the LD, anaperture R provided on the stage 6, and a periphery S which is theperipheral portion of the stage 6 are extended concentrically about theoptical axis L, as it is shown in FIG. 4.

Herein, the configuration of each of the apertures P, Q and R as well asthe periphery S can be, but is not limited to, a circle illustrated inFIG. 4.

Placing the wavelength converting member 2 on the stage 6 can increasethe contacting area between the wavelength converting member 2 and thesupport member 3 (particularly the stage 6) with comparative easiness.Thereby, a heat dissipation route from the wavelength converting member2 to the support member 3 can be ensured, and therefore, the lightemitting device having further excellent heat dissipation and heatresistance can be obtained.

The light transmissive member 4 a can be configured to partially contactwith the support member 3 on the stage 6, as it is illustrated in FIG.3.

Thereby, the contacting area between the light transmissive member 4 aand the support member 3 can be increased with a comparative easiness.Accordingly, the light transmissive member 4 a can be fixed more tightlyto the support member 3 by fusion bonding.

The material to form the base portion 7 and/or the sleeve portion 8 ofthe support member 3 is not particularly limited, but those having athermal expansion coefficient similar to that of the light transmissivemember 4 are preferable.

Besides, the material having an excellent radiation property ispreferable.

Such material can be, typically, a metal (e.g., iron, nickel, cobalt,aluminium) and alloy thereof (e.g., stainless steel, Ni—Fe alloy,Kovar), etc.

Among these, it is preferable to use Kovar or aluminium because of itsthermal expansion coefficient.

Herein, a reflective coat comprising a material including silver can beapplied on the support member 3, particularly on the surface of theinner wall of the through-hole 5.

Therefore, the extract efficiency of the light can be further improved.

The support member 3 can be prepared form the above-described materialaccording to the conventionally known method (e.g., press processing,machining, or the like).

Other Components

Herein, in the first embodiment of the light emitting device 10according to the present invention, an optical fiber 13 can be providedbetween the LD and the wavelength converting member 2, as it isillustrated in FIG. 1.

Thereby, the light emitted from the LD can be radiated through theoptical fiber 13 to the wavelength converting member 2 in order toilluminate the wavelength converting member 2.

Therefore, the relative positional relation between them can becomparatively and optionally designed.

The optical fiber 13 can be composed of a material including, forexample, glass, preferably quartz glass, resin, etc.

Furthermore, as shown in FIG. 2, one end portion of the optical fiber 13(i.e., an end of the optical fiber 13, which is a side directed to thewavelength converting member 2) may have an adaptor 14 to be engaged andconnected to the inner space of the sleeve portion of the support member3.

Another end portion of the optical fiber 13 (i.e., an end of the sidedirected to the LD) may have a connector 12 to facilitate the connectionbetween the optical fiber 13 and the LD or a device comprising the LD,as it is illustrated in FIG. 1.

Furthermore, regarding the end face of the optical fiber 13, which isdirected to the LD, a lens 11 may be provided between the end face ofthe optical fiber 13, which is directed to the LD, and the LD, in orderto collect the light emitted from the LD, as it is illustrated in FIG.1.

The lens 11 can be that enabling the light emitted from the LD to becollected on the end face of the optical fiber 13.

Herein, the light emitting device according to the first embodiment ofthe present invention is configured as it is described above, but thelight emitting device according to the present invention is notparticularly limited to the configuration of this first embodiment.

Second Embodiment

The light emitting device 20 according to the second embodiment of thepresent invention is similar to the device illustrated in FIG. 1 exceptthe configurations around the support member 3.

Specifically, as it is illustrated in FIG. 5, the shape of each of thewavelength converting member 2, the support member 3 and the lighttransmissive members 4 a and 4 b is different from that of the firstembodiment shown in FIG. 3.

In the embodiment shown in FIG. 5, any stage 6 as it is illustrated withrespect to the first embodiment shown in FIG. 3 is not provided on theinside of the through-hole of the support member 3, but a taperedsurface is provided on all the inner area.

Other configurations are similar to those described in the first lightemitting device.

In this second embodiment, providing the tapered surface on all the areaof the inner wall of the through-hole 5 can increase the attached areaby the fusion bonding between the light transmissive members 4 a and 4 band the support member 3, and thus the wavelength converting member 2can be fixed more tightly thereto.

Herein, such tapered surface can prevent the light from going backward.The angle of the created taper surface is not particularly limited, andoptionally, depending on the desired application, it can beappropriately determined.

Herein, dimensions and shapes of the wavelength converting members 2 aswell as the light transmissive members 4 a and 4 b can be adjustedcorresponding to the shape of the tapered surface.

In the second light emitting device, it is preferable that thewavelength converting member 2 as well as the light transmissive members4 a and 4 b are positioned coaxially about the optical axis L.

For example, as it is illustrated in the top view of FIG. 6, it ispreferable that an aperture P of the through-hole provided in thesupport member 3, which is directed to the LD; an aperture Q of thethrough-hole provided in the support member 3, which is opposed to theLD; a periphery T of the wavelength converting member 2, which isdirected to the LD; and a periphery U of the wavelength convertingmember 2, which is opposed to the LD; have any shapes and dimensions,respectively, such that these are extended concentrically about theoptical axis L.

It is preferable that the periphery of the light-entering side of thelight transmissive member 4 a approximately corresponds to the peripheryU of the light-extracting side of the wavelength converting member 2,and these peripheries preferably have substantially the same shape anddimension.

It is preferable that the periphery of the light-extracting side of thelight transmissive member 4 a approximately corresponds to the apertureQ of light-extracting side of the through-hole provided in the supportmember 3, and these preferably have substantially the same shape anddimension.

It is preferable that the periphery of the light-entering side of thelight transmissive member 4 b approximately corresponds to the apertureP of the light-entering side of the through-hole provided in the supportmember 3, and these preferably have substantially the same shape anddimension.

It is preferable that the periphery of the light-extracting side of thelight transmissive member 4 b approximately corresponds to the peripheryT of the light-entering side of the wavelength converting member 2, andthese preferably have substantially the same shape and dimension.

Third Embodiment

The light emitting device 30 according to the third embodiment of thepresent invention is similar to that of the light emitting device shownin FIG. 1 as a whole.

Specifically, as it is illustrated in FIG. 7, the shapes of thewavelength converting member 2, the support member 3, and the lighttransmissive member 4 a are respectively different from those of thefirst embodiment shown in FIG. 3.

In the embodiment illustrated in FIG. 7, the whole inner wall of thethrough-hole provided in the support member 3 has a tapered surfacewithout the stage 6 provided in the first embodiment shown in FIG. 3.

Furthermore, in this embodiment, the light transmissive member 4 b whichcan be employed in the first embodiment is not provided, but only thelight transmissive member 4 a is placed.

Other configurations are similar to those of the above-described lightemitting device of the first embodiment.

Herein, the wavelength converting member 2, the support member 3 and thelight transmissive member 4 a, which are illustrated in FIG. 7, may havesubstantially same shapes to those illustrated in FIG. 5 and FIG. 6.

Herein, the dimensions may be identical or different from thoseillustrated in FIG. 5 and FIG. 6.

Such configurations enable the light transmissive member 4 a to fix thewavelength converting member 2 to the support member 3.

In this embodiment, output power can be further improved since the lightemitted from the LD directly irradiates the wavelength converting member2 although color unevenness may be occurred as the light transmissivemember 4 b is not provided.

In this embodiment, at an area where the light transmissive member 4 bis not provided in the through-hole, the wavelength converting member 2could not be fallen down from the through-hole to the downward since thethrough-hole is tapered and narrowed toward the LD.

Fourth Embodiment

The light emitting device 40 according to the fourth embodiment of thepresent invention is similar to that of the light emitting device shownin FIG. 1 as a whole.

Specifically, as it is illustrated in FIG. 8, the light transmissivemember 4 b which can be employed in the first embodiment shown in FIG. 3is not provided, but only the light transmissive member 4 a is providedas the light transmissive member.

Other configurations are similar to those of the above-described lightemitting device according to the first embodiment.

Such configurations enable the light transmissive member 4 a to fix thewavelength converting member 2 to the support member 3.

Herein, at the area where the light transmissive member 4 b is notpresented in the through-hole, the through-hole is narrowed. Therefore,the wavelength converting member 2 could not be fallen down from thethrough-hole at that lower area.

Fifth Embodiment

The light emitting device 50 according to the fifth embodiment of thepresent invention is similar to that of the light emitting device shownin FIG. 1 as a whole.

However, specifically, as it is illustrated in FIG. 9, the shapes of thewavelength converting member 2, the support member 3 and the lighttransmissive member 4 b are respectively different from those of thefirst embodiment shown in FIG. 3.

Besides, in the embodiment illustrated in FIG. 9, the whole inner wallof the through-hole of the support member 3 has a tapered surfacewithout the stage 6 provided in the first embodiment shown in FIG. 3.

Furthermore, in this embodiment, the light transmissive member 4 a whichcan be employed in the first embodiment illustrated in FIG. 3 is notprovided, and therefore, the surface A of the wavelength convertingmember 2 is the light emitting surface.

Additionally, only the light transmissive member 4 b is provided as thelight transmissive member.

Other configurations are similar to those of the above-described lightemitting device according to the first embodiment.

Herein, the wavelength converting member 2, the support member 3, andthe light transmissive member 4 b, which are illustrated in FIG. 9,respectively, may have the same shapes to those illustrated in FIG. 5and FIG. 6.

Herein, the dimensions may be identical or different from thoseillustrated in FIG. 5 and FIG. 6.

Such configurations enable the light transmissive member 4 b to fix thewavelength converting member 2 to the support member 3.

In such a case, the light transmissive member 4 b and the wavelengthconverting member 2 are fixed to each other by the fusion bonding of thelight transmissive member 4 b.

Sixth Embodiment

The light emitting device 60 according to the sixth embodiment of thepresent invention is similar to that of the light emitting device shownin FIG. 1 as a whole.

However, specifically, as it is illustrated in FIG. 10, the lighttransmissive member 4 a which can be employed in the first embodimentshown in FIG. 3 is not provided, and therefore, the surface A of thewavelength converting member 2 is the light emitting surface.

Additionally, only the light transmissive member 4 b is provided as thelight transmissive member.

Other configurations are similar to those of the above-described lightemitting device according to the first embodiment.

Such configurations enable the light transmissive member 4 b to fix thewavelength converting member 2 to the support member 3.

In such a case, the light transmissive member 4 b and the wavelengthconverting member 2 are fixed to each other by the fusion bonding of thelight transmissive member 4 b.

Other Embodiments

FIG. 11 illustrates a cross-sectional schematic view for describing theconfigurations of the light emitting device 70 according to the one ofthe other embodiments of the present invention.

As it is described in FIG. 11, the components such as the lens 11, theconnector 12, the optical fiber 13 and the adaptor 14 which can beemployed in the above-described embodiment are not provided between thelaser diode 1 and the wavelength converting member 2.

The laser diode 1 is provided in the inner space 19 inside the sleeveportion 8 of the support member 3.

Other components and configurations thereof are substantially similar tothose of the light emitting devices described in the above-describedfirst to sixth embodiments.

In this embodiment, the laser diode 1 can be fixed to a stem 15 in ashape of a plate, optionally, using a heat sink 18, and the inner space19 of the sleeve portion 8 can be sealed by the stem 15.

A plurality of leads 16 a, 16 b are provided to the stem 15 in order toelectrically connect to an external power source, which leads areprovided through a plurality of through-holes provided in the stem 15,respectively.

These through-holes can be further sealed with sealing materials 17 a,17 b each of which comprise a material such as a low melting glass.

Herein, the laser diode 1 can be electrically connected to the lead 16a, 16 b, respectively, via a conductive member such as a wire.

Such configurations of this embodiment may preferably include theconfigurations of the above-described first to sixth embodimentsillustrated in FIG. 3 to FIG. 10, for example.

Herein, the wavelength converting member 2 and the support member 3 canbe adjusted to satisfy the certain relation to provide the similarresults.

Although, in this embodiment, other components are not presented betweenthe laser diode 1 and the wavelength converting member 2 or the lighttransmissive member 4 b, for example, other component such as lensenabling to collect the laser light can be provided between them.

INDUSTRIAL APPLICABILITY

The light emitting device according to embodiments of the presentinvention can be utilized in various applications requiring a light withan improved higher output power, particularly applications requiring awhite light having an improved higher output power.

The light emitting device according to embodiments of the presentinvention can be used, for example, as a lighting device for anendoscope, a fiber scope, etc.

In addition, the light emitting device according to embodiments of thepresent invention can be utilized in a lighting system used for indooror outdoor applications, a lighting system for a vehicle, specificallyfor a headlight, and the like, as a light source.

EXPLANATIONS OF LETTERS OR NUMERALS

-   -   1: laser diode (LD)    -   2: wavelength converting member    -   3: support member    -   4: light transmissive member    -   4 a: light transmissive member which is disposed on one surface        of the wavelength converting member, which surface is opposed to        another surface directed to a laser diode    -   4 b: light transmissive member which is disposed on the surface        of the wavelength converting member, which surface is directed        to the laser diode    -   5: through-hole    -   6: stage    -   7: base portion    -   8: sleeve portion    -   10: first embodiment of the light emitting device according to        the present invention    -   11: lens    -   12: connector    -   13: optical fiber    -   14: adaptor    -   15: stem    -   16 a: lead    -   16 b: lead    -   17 a: sealing material    -   17 b: sealing material    -   18: heat sink    -   19: inner space    -   20: second embodiment of the light emitting device according to        the present invention    -   30: third embodiment of the light emitting device according to        the present invention    -   40: fourth embodiment of the light emitting device according to        the present invention    -   50: fifth embodiment of the light emitting device according to        the present invention    -   60: sixth embodiment of the light emitting device according to        the present invention    -   70: other embodiment of the light emitting device according to        the present invention    -   A: one surface of the wavelength converting member (or surface        A), which surface is opposed to another surface directing to the        laser diode    -   B: another surface of the wavelength converting member (or        surface B), which surface is directed to the laser diode    -   L: optical axis    -   P: aperture on the base portion of the support member at a side        directing to LD (or at a side to which a light travels)    -   Q: aperture on the base portion of the support member at a side        opposed to the side directing to LD (or at a side from which a        light travels)    -   R: aperture on stage 6    -   S: periphery of stage 6    -   T: periphery of wavelength converting member 2 being at a side        directing to LD (or at a side to which a light travels)    -   U: periphery of wavelength converting member 2 being at a side        opposed to the side directing to LD (or at a side from which a        light travels)

What is claimed is:
 1. A light emitting device comprising: a laserdiode; a wavelength converting member which is configured to convert awavelength of a light emitted from the laser diode; and a support memberwhich has a through-hole, and which is configured to support thewavelength converting member so that the light passes through twosurfaces of the wavelength converting member in the through-hole,wherein: the wavelength converting member comprises a fluorescentmaterial and a binder, a light transmissive member is disposed on onesurface of the wavelength converting member, which surface is opposed toanother surface which is directed to the laser diode, the binder has amelting point higher than a melting point of the light transmissivemember, the light transmissive member is fixed to an inner wall of thethrough-hole of the support member and the surface of the wavelengthconverting member, which surface is opposed to the surface which isdirected to the laser diode, by fusion bonding.
 2. The light emittingdevice according to claim 1, wherein a difference between the meltingpoint of the binder and the melting point of the light transmissivemember is within a range from 500° C. to 2500° C.
 3. The light emittingdevice according to claim 1, wherein the binder has a melting point of1000° C. to 3000° C.
 4. The light emitting device according to claim 1,wherein the binder is made of at least one selected from the groupconsisting of aluminium oxide, silicon dioxide, zirconium oxide, bariumoxide and titanium oxide.
 5. The light emitting device according toclaim 4, wherein the binder is made of aluminium oxide.
 6. The lightemitting device according to claim 1, wherein the light transmissivemember has a melting point of 200° C. to 1000° C.
 7. The light emittingdevice according to claim 1, wherein the light transmissive member ismade of at least one selected from the group consisting of soda glass,borosilicate glass and lead glass.
 8. The light emitting deviceaccording to claim 7, wherein the glass is borosilicate glass.
 9. Thelight emitting device according to claim 1, wherein the wavelengthconverting member comprises a light scattering member.
 10. The lightemitting device according to claim 1, wherein the light transmissivemember comprises a light scattering member.
 11. A light emitting devicecomprising: a laser diode; a wavelength converting member which isconfigured to convert a wavelength of a light emitted from the laserdiode; and a support member which has a through-hole, and which isconfigured to support the wavelength converting member so that the lightpasses through two surfaces of the wavelength converting member in thethrough-hole, wherein: the wavelength converting member comprises afluorescent material and a binder, a light transmissive member isdisposed on one surface of the wavelength converting member, whichsurface is directed to the laser diode, the binder has a melting pointhigher than a melting point of the light transmissive member, the lighttransmissive member is fixed to an inner wall of the through-hole of thesupport member and the surface of the wavelength converting member,which surface is directed to the laser diode, by fusion bonding.
 12. Thelight emitting device according to claim 11, wherein a differencebetween the melting point of the binder and the melting point of thelight transmissive member is within a range from 500° C. to 2500° C. 13.The light emitting device according to claim 11, wherein the binder hasa melting point of 1000° C. to 3000° C.
 14. The light emitting deviceaccording to claim 11, wherein the binder is made of at least oneselected from the group consisting of aluminium oxide, silicon dioxide,zirconium oxide, barium oxide and titanium oxide.
 15. The light emittingdevice according to claim 11, wherein the light transmissive member hasa melting point of 200° C. to 1000° C.
 16. The light emitting deviceaccording to claim 11, wherein the light transmissive member is made ofat least one selected from the group consisting of soda glass,borosilicate glass and lead glass.
 17. A light emitting devicecomprising: a laser diode; a wavelength converting member which isconfigured to convert a wavelength of a light emitted from the laserdiode; and a support member which has a through-hole, and which isconfigured to support the wavelength converting member so that the lightpasses through two surfaces of the wavelength converting member in thethrough-hole, wherein: the wavelength converting member comprises afluorescent material and a binder, each of two light transmissivemembers are disposed on both of the two surfaces of the wavelengthconverting member, respectively, the binder has a melting point higherthan a melting point of the light transmissive member, each of the lighttransmissive members is fixed to an inner wall of the through-hole ofthe support member and the surface of the wavelength converting memberby fusion bonding.
 18. The light emitting device according to claim 17,wherein a difference between the melting point of the binder and themelting point of the light transmissive member is within a range from500° C. to 2500° C.
 19. The light emitting device according to claim 17,wherein the binder has a melting point of 1000° C. to 3000° C.
 20. Thelight emitting device according to claim 17, wherein the binder is madeof at least one selected from the group consisting of aluminium oxide,silicon dioxide, zirconium oxide, barium oxide and titanium oxide. 21.The light emitting device according to claim 17, wherein the lighttransmissive member has a melting point of 200° C. to 1000° C.
 22. Thelight emitting device according to claim 17, wherein the lighttransmissive member is made of at least one selected from the groupconsisting of soda glass, borosilicate glass and lead glass.